Optical films and methods of making the same

ABSTRACT

In general, in a first aspect, the invent features a method, including providing a layer having a plurality of spaced-apart lines of a first material extending along a first direction and forming a line of a second material on opposing surfaces of each line of the first material, the first and second materials being different and adjacent lines of the second material being discontinuous. After forming the lines of the second material, forming pairs of spaced-apart lines of a third material between adjacent pairs of the lines of the second material, wherein each line of the third material is spaced apart from the closest line of the second material and the first and third materials are different.

TECHNICAL FIELD

This disclosure relates to optical films and related articles, systemsand methods.

BACKGROUND

Optical devices and optical systems are commonly used where manipulationof light is desired. Examples of optical devices include lenses,polarizers, optical filters, antireflection devices, retarders (e.g.,quarter-waveplates), and beam splitters (e.g., polarizing andnon-polarizing beam splitters). Optical devices can be in the form of afilm.

SUMMARY

In general, in a first aspect, the invent features a method, includingproviding a layer having a plurality of spaced-apart lines of a firstmaterial extending along a first direction and forming a line of asecond material on opposing surfaces of each line of the first material,the first and second materials being different and adjacent lines of thesecond material being discontinuous. After forming the lines of thesecond material, forming pairs of spaced-apart lines of a third materialbetween adjacent pairs of the lines of the second material, wherein eachline of the third material is spaced apart from the closest line of thesecond material and the first and third materials are different.

Embodiments of the method can include one or more of the followingfeatures and/or features of other aspects. For example, the lines of thefirst material can have a pitch of 500 nm or less (e.g., 200 nm or less,150 nm or less, 120 nm or less, 100 nm or less, 90 nm or less).

Forming the lines of the second material can include forming acontinuous layer of the second material on the layer comprising thelines of the first material, and removing portions of the continuouslayer of the second material to provide the lines of the secondmaterial. The continuous layer of the second material can be formedusing atomic layer deposition. The continuous layer of the secondmaterial can conform to the surface profile of the layer comprising theplurality of lines of the first material. Removing the portions of thecontinuous layer of the second material can include etching the layer ofthe second material. The etching can include reactive ion etching.

In some embodiments, the second material is a dielectric material. Thesecond material can be an oxide material. The second material can have arefractive index of 1.8 or more and an extinction coefficient of 1.8 ormore for a wavelength λ that is 400 nm or less.

The lines of the second material can have a line width of 100 nm or less(e.g., 75 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nmor less, 10 nm or less). The lines of the second material can have athickness of 50 nm or more (e.g., 75 nm or more, 100 nm or more, 125 nmor more, 150 nm or more, 175 nm or more, 200 nm or more). The lines ofthe second material can have an aspect ratio of 5:1 or more (e.g., 10:1or more, 15:1 or more, 20:1 or more).

In some embodiments, forming the lines of the second material caninclude forming lines of a fourth material adjacent the lines of thesecond material, wherein the second and fourth materials are differentand the adjacent lines of the second and fourth material form compoundgrating lines and the compound grating lines are spaced apart from thelines of the third material.

In certain embodiments, forming the lines of the third material includesforming a continuous layer of a fourth material over the lines of thesecond material and forming a layer of the third material over the layerof the fourth material, wherein the second and third materials aredifferent from the fourth material. Forming the lines of the thirdmaterial can further include removing portions of the continuous layerof the third material to provide the lines of the third material.

The third material can be a dielectric material. The third material canbe an oxide material. The third material can be the same as or differentfrom the second material.

The second material can have a refractive index of 1.8 or more and anextinction coefficient of 1.8 or more for a wavelength λ that is 400 nmor less.

The lines of the third material can have a line width of 100 nm or less(e.g., 75 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nmor less, 10 nm or less).

In some embodiments, the lines of the second material and the lines ofthe third material have the same line width. The lines of the thirdmaterial can have a thickness that is different from a thickness of thelines of the second material. The thickness of the lines of the secondmaterial can be greater than the thickness of the lines of the thirdmaterial.

In some embodiments, forming the lines of the third material can includeforming lines of a fourth material adjacent the lines of the thirdmaterial, wherein the third and fourth materials are different and theadjacent lines of the third and fourth material form compound gratinglines and the compound grating lines are spaced apart from the lines ofthe second material.

In some embodiments, the method further includes depositing fifthmaterial over the lines of the third material, wherein the firstmaterial and the third material are different. The first material can bethe same as or different from the fifth material. The fifth material canbe a dielectric material. The fifth material can be deposited usingatomic layer deposition. Depositing the fifth material can fill spacesbetween adjacent lines of the third material. Depositing the fifthmaterial can form a monolithic layer including the fifth material, thelines of the second material, and the lines of the third material.

Providing the layer having the lines of the first material can includeproviding a substrate supporting the lines of the first material, thesubstrate comprises a substrate material. The first material andsubstrate materials can be different. Alternatively, the first materialand substrate materials can be the same. The substrate material can be adielectric material.

Proving the layer having the lines of the first material can includeproviding a continuous layer of the first material and removing portionsof the first material from the continuous layer to provide the lines ofthe first material.

The first material can be a dielectric material. The first material canbe silica.

The lines of the second and third materials can form a grating thattransmits 20% or more of light of wavelength λ having a firstpolarization state incident on the layer along a path, transmits 2% orless of light of wavelength λ having a second polarization stateincident on the layer along the path, the first and second polarizationstates being orthogonal, and λ is 400 nm or less. In some embodiments,the grating transmits 50% or more (e.g., 60% or more, 70% or more, 80%or more) of light of wavelength λ having the first polarization state.The grating can transmit 1% or less (e.g., 0.5% or less, 0.2% or less,0. 1% or less) of light of wavelength λ having the second polarizationstate. The grating can have an extinction ratio of 20 dB or more (e.g.,25 dB or more, 30 dB or more) for light at λ transmitted by the grating.λ can be in a range from 100 nm to 400 nm. For example, λ is can beabout 266 nm, about 248 nm, about 193 nm, or about 157 nm.

The pairs of spaced-apart lines of the third materials can be formedbetween alternating pairs of the lines of the second material. The linesof the first material can be positioned between pairs of lines of thesecond material between which no lines of the third material are formed.

In general, in another aspect, the invention features a method,including forming a first conformal layer of a first material over afirst grating having a plurality of lines of the second materialdifferent from the first material, removing portions of the firstconformal layer to provide a second grating having lines of the firstmaterial, forming a second conformal layer of a third material over thesecond grating, and removing portions of the second conformal layer toprovide a third grating comprising lines of the third material and thelines of the first material. The third grating transmits 20% or more oflight of wavelength λ having a first polarization state incident on thelayer along a path, transmits 2% or less of light of wavelength λ havinga second polarization state incident on the layer along the path, thefirst and second polarization states being orthogonal, and λ is 400 nmor less. Embodiments of the method can include one or more features ofother aspects.

In general, in another aspect, the invention features an article,including a layer extending in a plane, the layer including a pluralityof spaced-apart lines of a first material extending along a firstdirection in the plane, each of the lines of the first material having athickness, t₁, along a second direction perpendicular to the plane, aplurality of spaced-apart lines of a second material extending along thefirst direction, each of the lines of the second material having athickness, t₂, along the second direction, t₂ being less than ti, andeach line of the second material being spaced-apart from a closest lineof the first material, wherein the first and second materials have arespective refractive index of 1.8 or more and a respective extinctioncoefficient of 1.8 or more for a wavelength λ that is 400 mn or less,and the layer transmits 20% or more of light of wavelength λ having afirst polarization state incident on the layer perpendicular to theplane, transmits 2% or less of light of wavelength λ having a secondpolarization state incident on the layer along the path, the first andsecond polarization states being orthogonal. Embodiments of the articlecan include one or more features of other aspects. Embodiments of thearticle can be produced using the aforementioned methods.

In another aspect, the invention features a system, including a lightsource configured to provide radiation at a wavelength λ duringoperation of the system, a support apparatus configured to position asubstrate to receive radiation provided by the light source, and apolarizer positioned between the light source and the target, thepolarizer comprising the article of aforementioned aspect.

In general, in another aspect, the invention features an article,including a layer extending in a plane, the layer including a pluralityof spaced-apart lines of a first material extending along a firstdirection in the plane, a plurality of spaced-apart lines of a secondmaterial extending along the first direction, each line of the secondmaterial being spaced-apart from a closest line of the first material,wherein the first and second materials are different and both have arespective refractive index of 1.8 or more and a respective extinctioncoefficient of 1.8 or more for a wavelength λ that is 400 nm or less,and the lines of the first material are arranged in pairs that alternatewith pairs of the lines of the second material, adjacent pairs of thefirst material are separated by 200 nm or less and adjacent pairs of thesecond material are separated by 200 nm or less. Embodiments of thearticle can include one or more features of other aspects. Embodimentsof the article can be produced using the aforementioned methods.

In another aspect, the invention features a system, including a lightsource configured to provide radiation at a wavelength λ duringoperation of the system, a support apparatus configured to position asubstrate to receive radiation provided by the light source, and apolarizer positioned between the light source and the target, thepolarizer comprising the article of aforementioned aspect.

In general, in a further aspect, the invention features an article,including a layer extending in a plane, the layer including a pluralityof spaced-apart lines of a first material extending along a firstdirection in the plane, each of the lines of the first material having athickness, t₁, along a second direction perpendicular to the plane, aplurality of spaced-apart lines of a second material extending along thefirst direction, each of the lines of the second material having athickness, t₂, along the second direction, t₂ being less than t₁, andeach line of the second material being spaced-apart from a closest lineof the first material, wherein the lines of the first material arearranged in pairs that alternate with pairs of the lines of the secondmaterial, adjacent pairs of the first material are separated by 200 nmor less and adjacent pairs of the second material are separated by 200nm or less, and the layer transmits 20% or more of light of wavelength λhaving a first polarization state incident on the layer perpendicular tothe plane, transmits 2% or less of light of a wavelength λ having asecond polarization state incident on the layer along the path, thefirst and second polarization states being orthogonal and λ being 400 nmor less. Embodiments of the article can include one or more features ofother aspects. Embodiments of the article can be produced using theaforementioned methods.

In another aspect, the invention features a system, including a lightsource configured to provide radiation at a wavelength λ duringoperation of the system, a support apparatus configured to position asubstrate to receive radiation provided by the light source, and apolarizer positioned between the light source and the target, thepolarizer comprising the article of aforementioned aspect.

Embodiments can include one or more of the following advantages.

For example, the methods can be used to form structures (e.g., periodicstructures) of relatively small size (e.g., small periods). For example,periodic structures with effective periods less than about 100 nm (e.g.,less than about 80 nm, less than about 60 nm, less than about 40 nm,less than 30 nm) can be formed. The structures do not significantlydiffract optical radiation at wavelengths larger than the effectiveperiod of the structures. Thus, the structures formed using the methodsdisclosed herein can be used in optical devices and systems thatmanipulate short-wavelength optical radiation.

Effectively periodic structures with successively smaller effectiveperiods can be formed by repeating the method steps. For example,multiple sacrificial layers can be provided in a starting multilayerarticle. Each sacrificial layer can be used to produce an effectivelyperiodic structure with an effective period that is reduced by a factorof two relative to a periodic structure produced from a priorsacrificial layer, As a result, effectively periodic structures withrelatively small effective periods can be produced starting from aperiodic structure with a relatively large period.

The methods can be used to form effectively periodic structures withoutthe use of a sacrificial layer. For example, photoresist layers exposedto form periodic pattern can provide a template for the deposition ofconformal coating layers. The deposited conformal coating layers canthen be selectively etched to produce an effectively periodic structurewith an effective period reduced by a factor of two relative to theperiod of the pattern in the photoresist layers. Forming effectivelyperiodic structures without use of a sacrificial layer reduces thenumber of method steps and reduces the amount of material used to formthe effectively periodic structures.

Conformal layers can be deposited using processes that providesubstantial control over the thickness of the conformal layer. Forexample, in some embodiments, conformal layers can be depositedmonolayer by monolayer, allowing for thickness control on the order ofone monolayer. For example, atomic layer deposition can be used to formconformal layers. Accurate control of the conformal layer thickness canallow for more accurate control over the fidelity of etch masks formedusing methods disclosed herein.

The methods can be used to form structures from a variety of materials.Accordingly, the methods can be used to form a variety of differentdevices, such as different optical devices. As an example, materials,such as aluminum, that have relatively low transmission in certainregions of the electromagnetic spectrum, such as the deep ultravioletregion, can be used to form polarizers which operate in these regions ofthe spectrum. As another example, materials, such as dielectricmaterials, that have relatively high transmission in certain regions ofthe electromagnetic spectrum, such as the deep ultraviolet region, canbe used to form retarders which operate in these regions of thespectrum.

In certain aspects, grating layers formed from materials with arefractive index and extinction coefficient of 1.5 or more at awavelength λ can be used as a polarizer for radiation at λ. It isbelieved that absorption at λ (e.g., in the UV) by the material formingthe gratings generates the polarization effect. This aspect can differfrom a conventional wire-grid polarizer which typically utilizesmaterials with high reflectivity at the operating wavelength.

Certain materials with refractive indexes and extinction coefficients of1.5 or more (e.g., TiO₂ and W) can be deposited using atomic layerdeposition. This deposition method can be used to form gratings withshort effective periods, narrow line widths, and high aspect ratios,suitable for polarizing radiation in the UV portion of theelectromagnetic (EM) spectrum.

Because of the absorption principle, it is believed that the width ofthe portions forming the polarizing structure should be very thin inorder to avoid excessive absorption of the pass state light. Forexample, for certain embodiments configured to polarize UV radiation,the gratings may have an effective period of about 150 nm or less (e.g.,about 100 nm or less), while the portions forming the grating may have awidth of about 10 nm to 15 nm to provide sufficient pass statetransmission, whereas for widths of 30 nm to 40 nm or more, the passstate transmission can be unacceptably low for certain targetapplications.

Among other advantages, embodiments disclosed herein can includepolarizer films for use in the UV portion of the EM spectrum.Embodiments include polarizer films that feature gratings formed frommaterials that absorb radiation at the operating wavelength(s).

The polarizer films can exhibit good resistance to environmentaldegradation. For example, compared to polarizers formed from materialswhich can oxidize over time thereby degrading performance, embodimentscan include polarizer films formed from materials which don't oxidize inthe same way, for example, the metal grid lines do in certain wire gridpolarizers. The environmental resistance can be especially pronouncedfor polarizer gratings in which the material used to form the gratinghas a high surface to volume ratio, for example, gratings having verynarrow line widths (e.g., line widths of about 50 nm or less) and/orhigh aspect ratios.

Good resistance to environmental degradation can be achieved usingmonolithic grating layers. A cap layer can also be provided toencapsulate the grating layer, reducing any exposure of the gratinglayer to environmental elements. In some embodiments, monolithic gratinglayers having relatively high extinction ratios and/or relatively highpass state transmission can be provided. For example, polarizer filmsare provided that are formed by depositing more than two grating lineson each line of a larger period sacrificial grating structure. This canallow formation of high aspect ratio gratings having extremely shorteffective grating periods. Such structures can exhibit improved opticalperformance (e.g., higher extinction ratios and/or higher pass statetransmission) relative to monolithic grating layers formed by depositingonly two grating lines per each line of the sacrificial gratingstructure.

Embodiments include broadband polarizers operational in the UV andvisible portions of the spectrum. For example, in some embodiments,gratings are formed from materials that absorb and/or reflect radiationacross a broad spectrum, including portions of the UV and visibleportions of the spectrum. For example, gratings formed from Tungsten canbe used for polarization of UV and visible wavelengths. In certainembodiments, polarizers can include gratings formed from two or moredifferent materials, where one material is selected to providepolarization in one region of the EM spectrum, while another material isselected to provide polarization in a different region of the EMspectrum. For example, polarizers can include a grating formed from TiO2and a grating formed from a metal, such as aluminum. The TiO₂ gratingprovides polarization in the 200 nm to 310 nm range, and the aluminumgrating provides polarization in the visible.

In certain embodiments, polarizer films can be configured to polarizeradiation in the infrared (IR) region of the EM spectrum (e.g., in arange from about 1,200 nm to about 2,000 nm).

Other features and advantages of the invention will be apparent from thedescription, drawings, and claims.

DESCRIPTION OF DRAWINGS

FIG. 1A is a cross-sectional view of an embodiment of a polarizer film.

FIG. 1B is a plan view of an embodiment of a polarizer film.

FIG. 1C is a cross-sectional view of the polarizer film shown in FIG.1A.

FIG. 1D is a cross-sectional view of an embodiment of a polarizer film.

FIG. 1E is a plot of simulated extinction ratio as a function ofwavelength for an embodiment of a linear polarizer film.

FIG. 1F is a plot of simulated total pass state transmission andreflection as a function of wavelength for an embodiment of a linearpolarizer film.

FIG. 1G is a plot of simulated pass state transmission as a function ofwavelength for an embodiment of a linear polarizer film.

FIG. 2A-2J are cross-sectional views of an article during variousprocess steps in an implementation of a process for making a linearpolarizer film.

FIG. 3 is a schematic diagram of a system for performing atomic layerdeposition.

FIG. 4 is a flowchart showing steps in an atomic layer depositionmethod.

FIG. 5 is a cross-sectional view of an embodiment of a polarizer film.

FIG. 6 is a cross-sectional view of an embodiment of a polarizer film.

FIGS. 7A and 7B are a cross-sectional views of an embodiment of apolarizer film.

FIG. 8 is a schematic diagram of a system utilizing a linear polarizerfilm.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring to FIGS. 1A-1C, a linear polarizer film 100 includes a gratinglayer 110, a substrate layer 120, and a cap layer 130. A Cartesianco-ordinate system is shown for reference. Grating layer 110 linearlypolarizes incident light of wavelength λ₁ propagating parallel to thez-axis. In other words, for light of wavelength λ₁ incident on linearpolarizer film 100 propagating parallel to the z-axis, linear polarizerfilm 100 transmits a relatively large amount of the component ofincident light plane-polarized in the x-direction (referred to as “pass”state polarization) compared to the amount of the componentplane-polarized in the y-direction (referred to as “block” statepolarization). For example, polarizer film 100 can transmit about 25% ormore (e.g., about 30% or more, about 40% or more, about 50% or more,about 60% or more, about 80% or more) of pass state light at λ₁ whilepassing about 5% or less of the block state light (e.g., about 4% orless, about 3% or less, about 2% or less, about 1% or less, about 0.5%or less, 0.3% or less, 0.2% or less, 0.1% or less) at λ₁. In someembodiments, transmission of pass state radiation can be less than 25%at λ₁ (e.g., about 10%, about 15%, about 20%), while still beingsignificantly more than the block state transmission. λ₁ can correspondto a local (or global) maximum in the pass state transmission spectrum.Alternatively, or additionally, λ₁ can correspond to a local (or global)minimum in the block state transmission spectrum.

In general, λ₁ is between about 100 nm and about 5,000 nm. In certainembodiments, λ₁ corresponds to a wavelength within the visible portionof the EM spectrum (e.g., from 400 nm to 700 nm). In some embodiments,λ₁ corresponds to a wavelength in the UV portion of the EM spectrum(e.g., from about 100 nm to about 400 nm, from about 150 mn to about 350nm, from about 200 nm to about 300 nm, about 250 nm, 266 nm).

In some embodiments, linear polarizer film 100 polarizes radiation atmore than one wavelength. For example, linear polarizer film 100 canpolarize radiation at wavelengths λ₁ and λ₂, where λ₁<λ₂ and |λ_(1−λ) ₂|is about 50 nm or more (e.g., about 75 nm or more, about 100 nm or more,about 150 nm, about 200 nm or more, about 250 nm or more, about 300 nmor more, about 400 nm or more, about 500 nm or more). λ₂ can correspondto a local (or global) maximum in the pass state transmission spectrum.Alternatively, or additionally, λ₂ can correspond to a local (or global)minimum in the block state transmission spectrum.

In certain embodiments, linear polarizer film 100 can polarize radiationfor a continuous band of wavelengths, Δλ, that includes λ₁ and λ₂. Forexample, linear polarizer film 100 can polarize radiation for a band ofwavelengths, Δλ, about 10 nm wide or more (e.g., about 20 nm wide ormore, about 50 nm wide or more, about 80 nm wide or more, about 100 nmor more, about 200 nm or more, about 300 nm or more, about 400 nm ormore). In some embodiments, linear polarizer film 100 can polarize aband of wavelengths in the UV portion of the EM spectrum. For example,linear polarizer film 100 can polarize radiation from 200 nm to 300 nm.In certain embodiments, linear polarizer film 100 polarizes radiation at266 nm, at 248 nm, at 193 nm, and/or at 157 nm.

Furthermore, while linear polarizer film 100 polarizes incidentradiation propagating parallel to the z-axis, in some embodiments,polarizer film 100 can polarize radiation at λ₁ for radiation atnon-normal angles of incidence (i.e., for radiation incident on linearpolarizer film 100 propagating at an angle θ with respect to the z-axis,where θ is non-zero). In certain embodiments, linear polarizer film 100can polarize radiation incident at more than one angle of incidence,such as for a range of incident angles. For example, in someembodiments, linear polarizer film 100 polarizes radiation incidentwithin a cone of incident angles for θ of about 10° or more (e.g., about15° or more, about 20° or more, about 30° or more, about 45° or more).Note that for non-normal incidence, the pass state corresponds to lightpolarized parallel to the x-z plane, while the block state correspondsto light polarized orthogonal to the x-z plane.

In embodiments, linear polarizer film 100 blocks a relatively largeamount of incident radiation at λ₁ and/or λ₂ having the block statepolarization by absorbing a relatively large amount of the block stateradiation. For example, linear polarizer film 100 can absorb about 80%or more of incident radiation at λ₁ and/or λ₂ having the blockpolarization state (e.g., about 90% or more, about 95% or more, about98% or more, about 99% or more). In some embodiments, block statereflection from polarizer film 100 is relatively low. For example,polarizer film 100 can reflect about 50% or less (e.g., about 20% orless, about 15% or less, about 10% or less, about 5% or less) ofincident block state radiation at λ₁. In certain embodiments, polarizerfilm 100 can reflect about 50% or less (e.g., about 20% or less, about15% or less, about 10% or less, about 5% or less) of incident blockstate radiation at λ₁ and λ₂. Alternatively, in some embodiments,polarizer film 100 can reflect about 50% or less (e.g., about 20% orless, about 15% or less, about 10% or less, about 5% or less) ofincident block state radiation at λ₁, while reflecting about 50% or more(e.g., about 60% or more, about 70% or more, about 80% or more, about90% or more) of incident block state radiation at λ₂.

Linear polarizer film 100 can have a relatively high extinction ratio,E_(T), for transmitted light at λ₁ and/or λ₂. For transmitted light, theextinction ratio refers to the ratio of pass state intensity at λ₁and/or λ₂ to the block state intensity transmitted by linear polarizerfilm 100. Extinction ratio is also referred to as polarizer contrast.E_(T) can be, for example, about 10 or more at λ₁ and/or λ₂ (e.g., about20 or more, about 30 or more, about 40 or more, about 50 or more, about60 or more, about 70 or more, about 80 or more, about 90 or more, about100 or more, about 150 or more, about 300 or more, about 500 or more).In some embodiments, λ₁ corresponds to a local (or global) maximum inthe extinction ratio as a function of wavelength, E_(T)(λ).Alternatively, or additionally, λ₂ can correspond to a local (or global)maximum in E_(T)(λ).

The extinction ratio of a polarizer can also be expressed in decibels(dB) rather than as a ratio, where the relationship between the ratioE_(T) and its corresponding dB value can be determined according to theequation:

E _(T.dB)=10·log₁₀ E _(T),

For example, an extinction ratio of 30 corresponds to approximately 15dB, an extinction ratio of 50 corresponds to approximately 17 dB, and anextinction ratio of 100 corresponds to 20 dB.

Linear polarizer film 100 can exhibit good resistance to degradation,e.g., due to exposure to environmental or operational factors. Suchfactors include, for example, humidity, heat, exposure to an oxidant(e.g., air), and/or radiation. In general, good resistance todegradation means that the optical performance (e.g., pass statetransmission, block state transmission, extinction ratio) of linearpolarizer film varies relatively little with prolonged exposure to oneor more of the environmental or operational factors. For example, inembodiments where linear polarizer film 100 is used as a polarizer forUV radiation, the polarizer film can exhibit little variation in opticalperformance over substantial periods (e.g., 100 hours or more, 500 hoursor more, 1,000 hours or more) of exposure to the radiation.

One way to characterize a linear polarizer's resistance to environmentaldegradation is by controlled environmental testing, such as exposure toan elevated temperature in a controlled atmosphere. As an example, alinear polarizer can subject to the test conditions and measurementcriteria summarized in Table 1. These Test conditions are in accordancewith section 6.2 of Telcordia GR-1221-CORE and in sections 4.1 and 4.2of Telcordia GR-1209-CORE, as referenced in Table I.

TABLE I Test Description Standard Reference Conditions Measurementafter: High Temperature Storage EIA/TIA-455-4A 6.2.4 85 ± 2° C. 2000hours (Dry Heat) <40% RH (5000 hours for info) High Temperature StorageEIA/TIA-455-5A 6.2.5 85 ± 2° C. 2000 hours (Damp Heat) 85 ± 5% RH LowTemperature Storage EIA/TIA-455-4A 6.2.6 −40 ± 5° C. 2000 hoursTemperature Cycling EIA/TIA-455-3A 6.2.7 −40 to +85° C. 500 cycles (1000cycles for info) Thermal Shock JESD22-A106-A, 6.2.3 0 to 100° C. 15cycles cond B

Linear polarizer films with good resistance to degradation exhibit avariation (e.g., increase or decrease) in transmittance at λ₁ of about8% or less (e.g., 5% or less, 4% or less, 3% or less, 2% or less, 1% orless) as measured before and after the exposure. Linear polarizer filmswith good resistance to degradation can also exhibit a variation (e.g.,increase or decrease) in E_(T) at λ₁ of about 8% or less (e.g., 5% orless, 4% or less, 3% or less, 2% or less, 1% or less) as measured beforeand after the exposure.

As a further example, another way to test environmental stability is byprolonged exposure to a high power UV emission source for extendedperiods. Specifically, a linear polarizer film can be tested bypositioning the polarizer 2 cm from a 1,000W Mercury Arc Lamp (e.g.,Model Code UVH 1022-0 available from Ushio America, Cypress, Calif.).The polarizer film is oriented so that light from the source is incidenton the polarizer along z-axis. E_(T) is measured at λ₁ before and afterexposure. Embodiments of linear polarizer films with good resistance todegradation can also exhibit a variation (e.g. ,increase or decrease) inE_(T) at λ₁ of about 8% or less (e.g., 5% or less, 4% or less, 3% orless, 2% or less, 1% or less) as measured before and after the exposure.

Turning now to the structure and composition of linear polarizer 100,grating layer 110 includes grating lines 112 and 114 that are separatedfrom one another along the x-direction and that extend along they-direction. Grating lines 112 and 114 are arranged in pairs. In otherwords, each pair of adjacent grating lines 112 are separated by a pairof grating lines 114, and vice-versa. As shown in FIG. 1C, adjacentgrating lines 112 are separated by portions 115, adjacent grating lines114 are separated by portions 111, and adjacent grating lines 112 and114 are separated by portions 113. Grating layer 110 is a monolithiclayer. In other words, there are no gaps between the different portionsand grating lines of the layer.

Each grating line and portion in grating layer 110 has a width measuredalong the x-direction. As shown in FIG. 1C, grating lines 112 have awidth w₁₁₂ and grating lines 114 have a width w₁₁₄. In general, w₁₁₂ andw₁₁₄ can be the same or different.

In general, w₁₂ and/or w₁₁₄ are less than λ₁. For example, w₁₁₂ and/orw114 can be about 0.2 λ₁ or less (e.g., about 0.1 λ₁ or less, about 0.05λ₁ or less, about 0.04 λ₁ or less, about 0.03 λ₁ or less, about 0.02 λ₁or less, 0.01 λ₁ or less). For example, in some embodiments, w₁₁₂ and/orw₁₁₄ is/are about 200 nm or less (e.g., about 150 nm or less, about 100nm or less, about 80 nm or less, about 70 nm or less, about 60 nm orless, about 50 nm or less, about 40 nm or less, about 30 nm or less). Insome embodiments, w₁₁₂ and/or w₁₁₄ is/are about 5 nm or more (e.g., 7 nmor more, 8 mn or more, 10 nm or more, 15 nm or more, about 20 nm ormore).

Portions 111 have a width w₁₁₁, portions 113 have a width w_(113,) andportions 115 have a width w₁₁₅. In general, widths w₁₁₁, w₁₁₃, and w₁₁₅can be the same or different.

W₁₁₁, w_(113,) and/or w₁₁₅ can be about 0.2 λ₁ or less (e.g., about 0.1λ₁ or less, about 0.05 λ₁ or less, about 0.04 λ₁ or less, about 0.03 λ₁or less, about 0.02 λ₁ or less, 0.01 λ₁ or less). For example, in someembodiments, w₁₁₁, w₁₁₃, and/or w₁₁₅ is/are about 200 nm or less (e.g.,about 150 nm or less, about 100 nm or less, about 80 nm or less, about70 nm or less, about 60 nm or less, about 50 nm or less, about 40 nm orless, about 30 nm or less). In certain embodiments, w₁₁₁, w_(113,)and/or w₁₁₅ is/are about 5 nm or more (e.g., 7 nm or more, 8 nm or more,10 nm or more, 15 nm or more, about 20 nm or more).

In some embodiments, w₁₁₃ can be approximately the same as w₁₁₂ and/orw₁₁₄. For example, in some embodiments, two or more of w₁₁₂, w₁₁₃, andw₁₁₄ are in a range from 5 nm to 15 nm.

Portions 111, 113, and 115 and grating lines 112 and 114 form arepeating structure having a pitch p₁₁₀, as shown in FIG. 1C. p₁₁₀equals w₁₁₁+2w₁₁₂+2w₁₁₃+2w₁₁₄+w₁₁₅. Grating lines 112 and 114 repeatwith an effective period, Λ, equal to p₁₁₀/4. In some embodiments, wherew₁₁₁=w₁₁₃=w₁₁₅ and w₁₁₂=w₁₁₄, grating lines 112 and 114 form a periodicstructure where the effective period is an actual period of the gratinglines.

In general, effective grating period, Λ, is smaller than λ₁ and as aresult light of wavelength λ₁ interacts with grating layer 110 withoutencountering significant high-order, far-field diffraction that canoccur when light interacts with periodic structures. Where λ₁ is in thevisible or UV portion of the EM spectrum, grating layer 110 can beconsidered an example of a nanostructured layer.

In general, Λ is less than λ₁, such as about 0.5 λ₁ or less (e.g., about0.3 λ₁ or less, about 0.2 λ₁ or less, about 0.1 λ₁ or less, about 0.08λ₁ or less, about 0.05 λ₁ or less, about 0.04 λ₁ or less, about 0.03 λ₁or less, about 0.02 λ₁ or less, 0.01 λ₁ or less). In some embodiments, Λis about 500 nm or less (e.g., about 300 nm or less, about 200 nm orless, about 150 nm or less, about 130 nm or less, about 100 nm or less,about 80 nm or less, about 60 nm or less, about 50 nm or less, about 40nm or less).

The duty cycle of grating layer 100, given by the ratio(2w₁₁₂+2w₁₁₄)/p₁₁₀, can vary as desired. In some embodiments, the dutycycle is less than about 50% (e.g., about 40% or less, about 30% orless, about 20% or less, about 10% or less, about 8% or less).Alternatively, in certain embodiments, the duty cycle is more than about50% (e.g., about 60% or more, about 70% or more, about 80% or more).

Grating layer 110 has a thickness t₁₁₀, measured along the z-direction.In general, the thickness, t₁₁₀, of grating layer 110 measured along thez-axis can vary as desired. In general, the thickness of layer 110 isselected based on the desired optical properties of grating layer 110 atλ₁ and constraints on the manufacturability of such structures. In someembodiments, t₁₁₀ can be about 50 nm or more (e.g., about 75 nm or more,about 100 nm or more, about 125 nm or more, about 150 nm or more, about200 nm or more, about 250 nm or more, about 300 nm or more, about 400 nmor more, about 500 nm or more, about 1,000 or more, such as about 2,000nm).

Grating lines 112 have a thickness t₁₁₂ and grating lines 114 have athickness t₁₁₄, both measured along the z-direction. t₁₁₂ is the same ast₁₁₀. t₁₁₄ is less than t₁₁₂ and t₁₁₀ by an amount t₁₁₆. For example, insome embodiments, t₁₁₄ is 98% or less of t₁₁₂ (e.g., 95% or less, 90% orless, 85% or less). In general, t₁₁₆ can be 5 nm or more (e.g., 7 nm ormore, 10 nm or more, 12 nm or more, 15 nm or more, 20 nm or more). Incertain embodiments, t₁₁₆ is equal to w₁₁₃.

In general, the dimensions (e.g., thicknesses and widths) of the gratinglines and portions separating the grating lines, and the materials fromwhich they are formed are selected based on the desired opticalproperties of linear polarizer 100.

In general, the number of grating lines 112 and 114 in a grating layermay vary as desired. The number of portions depends on the effectiveperiod, Λ, and the area required by the linear polarizer's end useapplication. In some embodiments, grating layer 110 can have about 50 ormore portions (e.g., about 100 or more portions, about 500 or moreportions, about 1,000 or more portions, about 5,000 or more portions,about 10,000 or more portions, about 50,000 or more portions, about100,000 or more portions, about 500,000 more portions).

The aspect ratio of grating layer thickness, t₁₁₀, to w₁₁₂ and/or t₁₁₀to w₁₁₄ can be relatively high. For example t₁₁₀:w₁₁₂ and/or t₁₁₀:w₁₁₄can be about 2:1 or more (e.g., about 3:1 or more, about 4:1 or more,about 5:1 or more, about 8:1 or more, about 10:1 or more, about 12:1 ormore, about 15:1 or more).

Turning to the composition of grating layer 110, in general, thecomposition of grating lines 112 and 114, and portions 111, 113, and 115are selected so that linear polarizer film 100 has desired polarizingproperties. The composition of grating lines 112 and 114 and portions111, 113, and 115 are also selected based factors such as theircompatibility with the manufacturing processes used in production ofpolarizer film 100 and their environmental properties, such asresistance to degradation due to environmental exposure.

In general, grating lines 112 and grating lines 114 can be formed fromthe same materials or from different materials. In embodiments, gratinglines 112 and 114 are formed from materials that have relatively lowtransmissivity at λ₁. A one micrometer thick bulk sample of a materialhaving relatively low transmissivity at λ₁ transmits less than about0.1% or less of radiation at λ₁ normally incident thereon (e.g., about0.05% or less, about 0.01% or less, about 0.001% or less, about 0.0001%or less). Low transmissivity materials include materials that absorb arelatively large amount of radiation at λ₁.

In some embodiments, for example, where λ₁ is in the UV portion of theEM spectrum, grating lines 112 and/or 114 can be formed from titaniumdioxide (TiO₂), tungsten (W), indium tin oxide (ITO), tantalum oxide(Ta₂O₅) molybdenum (Mo), indium phosphide (InP), gallium arsenide(GaAs), aluminum gallium arsenide (Al_(x)Ga_(1-x)As), silicon (Si)(e.g., crystalline, semi-crystalline, or amorphous silicon), indiumgallium arsenide (InGaAs), germanium (Ge), or gallium phosphide (GaP).

More generally, grating lines 112 and 114 can include inorganic and/ororganic materials. Examples of inorganic materials include metals,inorganic semiconductors, and inorganic dielectric materials (e.g.,glass). Examples of organic materials include polymers.

Grating lines 112 and/or 114 can be formed from materials that haverelatively high absorption at λ₁. A one micrometer thick bulk sample ofa material having a relatively high absorption absorbs about 90% or more(e.g., about 93% or more, about 95% or more) of radiation at λ₁ normallyincident thereon. In general, depending on λ₁, materials that have arelatively high absorption can include dielectric materials,semiconductor materials, and electrically-conducting materials.Dielectric materials that have a relatively high absorption for certainwavelengths in the UV, for example, include TiO₂. An example of asemiconductor material that has relatively high absorption for certainwavelengths in the UV is silicon (Si). Further examples of semiconductormaterials include Ge, indium phosphide (InP), and silicon-germanium(SiGe). Examples of electrically-conducting materials that have arelatively high absorption for certain wavelengths in the UV and visibleinclude cobalt (Co), platinum (Pt), and titanium (Ti). Other materialsinclude chromium (Cr), nickel (Ni), vanadium (V), tantalum (Ta),palladium (Pd), and iridium (Ir). Metal silicides, such as tungstensilicide (WSi₂), titanium silicide (TiSi), tantalum silicide (TaSi),hafnium silicide (HfSi₂), niobium silicide (NbSi), and chromium silicide(CrSi)) can also be used.

In some embodiments, grating lines 112 and/or 114 are formed from amaterial that have relatively low transmissivity at λ₂, such as amaterial that has a relatively low transmissivity across a band ofwavelengths including λ₁ and λ₂. For example, W has relatively lowtransmissivity over the wavelength range from about 200 nm to about 600nm and can be used to form a linear polarizer film that can be used overa relatively large range of wavelengths that include portions of the UVspectrum. In certain embodiments, the material forming grating lines 112and/or 114 has a relatively high absorption at λ₂.

In general, materials can be characterized by a complex index ofrefraction, ñ=n−ik, where n is the refractive index and k is theextinction coefficient. ñ, in general, varies as a function ofwavelength. Grating lines 112 and/or 114 can be formed from a materialthat has an extinction coefficient, k, of 1.5 or more (e.g., 1.8 ormore, 2 or more, 2.1 or more, 2.2 or more, 2.3 or more, 2.4 or more, 2.5or more, 2.6 or more, 2.7 or more, 2.8 or more, 2.9 or more, 3 or more,4 or more) at λ₁. In embodiments, k can be 5 or less (e.g., 4 or less,3.5 or less). In certain embodiments, k is in a range from 2 to 5. Forexample, W has a k value of 2.92 at about 633 nm. Additionally, in someembodiments, the material can have a refractive index, n, of 1.5 or more(e.g., 1.8 or more, 2 or more, 2.1 or more, 2.2 or more, 2.3 or more,2.4 or more, 2.5 or more, 2.6 or more, 2.7 or more, 2.8 or more, 2.9 ormore, 3 or more) at λ₁. As an example, W has a n value of 3.65 at about633 nm. As another example, TiO₂ has an n value of 2.88 at about 633 nm.

In certain embodiments, grating lines 112 and/or 114 are formed from amaterial that has an extinction coefficient, k, of 1.5 or more (e.g.,1.8 or more, 2 or more, 2.1 or more, 2.2 or more, 2.3 or more, 2.4 ormore, 2.5 or more, 2.6 or more, 2.7 or more, 2.8 or more, 2.9 or more, 3or more) at λ₂ as well as λ₁. The material can have a refractive index,n, of 1.5 or more (e.g., 1.8 or more, 2 or more, 2.1 or more, 2.2 ormore, 2.3 or more, 2.4 or more, 2.5 or more, 2.6 or more, 2.7 or more,2.8 or more, 2.9 or more, 3 or more) at λ₂.

In general, grating lines 112 and/or 114 include a single material.However, in certain embodiments, grating lines 112 and/or 114 can becompound grating lines, including layers of more than one material. Forexample, referring to FIG. 1D, in some embodiments, grating lines 114′are formed from layers of two different materials, indicated as 1141 and1142, respectively. The width (i.e., dimension in the x-direction) oflayers 1141 and 1142 can be the same or different. Compound gratinglines can be formed from layers of more than two materials.

As another example of compound grating lines, grating lines 112 and/or114 can be formed from a nanolaminate, which refers to a compositionthat is composed of layers of at least two different materials and thelayers of at least one of the materials are extremely thin (e.g.,between one and about 10 monolayers thick). Optically (e.g., at λ₁),nanolaminate materials have a locally homogeneous index of refractionthat depends on the refractive index of its constituent materials.Varying the amount of each constituent material can vary the refractiveindex of a nanolaminate. Examples of nanolaminate portions includeportions composed of silica (SiO₂) monolayers and TiO₂ monolayers, SiO₂monolayers and tantalum pentoxide (Ta₂O₅) monolayers, or aluminum oxide(Al₂O₃) monolayers and TiO₂ monolayers.

In general, grating lines 112 and/or 114 can include crystalline,semi-crystalline, and/or amorphous materials.

Turning now to the composition of portions 111, 113, and 115, ingeneral, these portions can be formed from the same material ordifferent portions can be formed from different materials. Generally,portions 111, 113, and/or 115 are formed from a material or materialsthat has a significantly higher transmissivity at λ₁ than thematerial(s) forming grating lines 112 and 114. For example, thetransmissivity of the material forming portions 111, 113, and/or 115 canbe about 100 times or more (e.g., about 500 times or more, about 103times or more, about 5×10³ times or more, about 10⁴ times or more)higher than the transmissivity of the material forming grating lines 112and 114. In some embodiments, portions 111, 113, and/or 115 are formedfrom SiO₂ (e.g., quartz), which is an example of a material that hasrelatively high transmissivity at visible wavelengths. Portions 111,113, and/or 115 can be formed from an inorganic glass (e.g., aboro-silicate glass) that has the desired properties at λ₁.

In certain embodiments, portions 111, 113, and/or 115 are formed from amaterial that has a relatively low transmissivity at λ₂. For example,portions 111, 113, and/or 115 can be formed from materials that haverelatively high absorption or reflectivity at λ₁.

The material forming portions 111, 113, and/or 115 can be selected sothat grating layer 110 linearly polarizes radiation at λ₂, while gratinglines 112 and 114 are formed from a material selected so that gratinglayer 110 linearly polarizes radiation at λ₁. As an example, in someembodiments grating lines 112 and 114 are formed from an oxide material(e.g., TiO₂) that has relatively high absorption in the UV (e.g., atapproximately 250 nm) while portions 111, 113, and/or 115 are formedfrom a metal (e.g., Al) that has relatively high reflectivity orabsorption in the visible (e.g., about 450 nm to about 700 nm) and/or IR(e.g., from 700 nm to about 2,000 nm).

In certain embodiments, portions 111, 113, and/or 115 are formed from amaterial that has an extinction coefficient, k, of 2 or more (e.g., 2.1or more, 2.2 or more, 2.3 or more, 2.4 or more, 2.5 or more, 2.6 ormore, 2.7 or more, 2.8 or more, 2.9 or more, 3 or more) at λ₂.Additionally, in some embodiments, the material can have a refractiveindex, n, of 2 or more (e.g., 2.1 or more, 2.2 or more, 2.3 or more, 2.4or more, 2.5 or more, 2.6 or more, 2.7 or more, 2.8 or more, 2.9 ormore, 3 or more) at λ₂.

In general, the structure and composition of grating layer 110 isselected based on the desired optical performance of linear polarizerfilm 100. Structural parameters that affect the optical performance oflinear polarizer 100 include, for example, t₁₁₀, t₁₁₄, w₁₁₁₋₁₁₅, and Λ.Typically, varying a single parameter affects multiple differentperformance parameters. For example, the overall transmittance of thepolarizer at λ₁ can be varied by changing the width of grating lines 112and 114 formed from a non-transmissive material, w₁₁₂ and w_(114,) tothe width of portions 111, 113, and 115. However, while a lower ratioof, e g., (w₁₁₂+w₁₁₄)/(w₁₁₁+2w₁₁₃+W₁₁₅) may provide relatively highertransmittance of the pass state polarization, it can also result inhigher transmittance of the block state polarization, which decreasesE_(T). As a result, optimizing the polarizer's performance involvestrade offs between different performance parameters and the polarizer'sstructure and composition is varied depending on the desired performancefor the polarizer's end use application.

To effectively polarize light at wavelength λ₁, the effective period Λof the grating layer should, in general, be shorter than λ₁, such asabout λ₁/4 or less (e.g., about λ₁/6 or less, about λ₁/10 or less).Moreover, for effective broadband performance, Λ should be shorter thanthe shortest wavelength in the wavelength band, Δλ. For a broadbandpolarizer in the visible spectrum, for example, Λ should be less thanabout 300 nm, such as about 200 nm or less (e.g., about 150 nm or less,about 130 nm or less, about 110 nm or less, about 100 nm or less, about90 nm or less, about 80 nm or less).

In some embodiments, E_(T) can be increased by increasing the thicknessof grating layer 110, t₁₁₀. Increasing t₁₁₀ can provide increased E_(T)without substantially reducing the amount of pass state transmittance.

Referring now to other layers in linear polarizer film 100, in general,substrate 120 provides mechanical support to polarizer film 100. In themanufacturing process of polarizer film 100, substrate layer 120 oftenforms a substrate for deposition of additional materials for forminggrating layer 110 and cap layer 130. In typical embodiments, wherepolarizer film 100 is a transmissive polarizer, substrate 120 istransparent to light at wavelength λ₁, transmitting substantially alllight impinging thereon at wavelength λ₁ (e.g., about 90% or more, about95% or more, about 97% or more, about 99% or more, about 99.5% or more).

In general, substrate 120 can be formed from any material compatiblewith the manufacturing processes used to produce polarizer 100 that cansupport the other layers. In certain embodiments, substrate 120 isformed from a glass, such as silica glass (e.g., fused quartz or fusedsilica, such as special UV grade fused silica), BK7 (available fromAbrisa Corporation), borosilicate glass (e.g., pyrex available fromComing), and aluminosilicate glass (e.g., C1737 available from Corning).In some embodiments, substrate 120 can be formed from a crystallinematerial, such as crystalline quartz or calcium fluoride (CaF₂), or, insome cases, a non-linear optical crystal (e.g., LiNbO₃ or amagneto-optical rotator, such as garnett) or a crystalline (orsemicrystalline) semiconductor (e.g., Si, InP, or GaAs). Substrate 120can also be formed from an inorganic material, such as a polymer (e.g.,a plastic).

In certain embodiments, substrate 120 is formed from the same materialas one or more of portions 111, 113, and/or 115. Embodiments in whichsubstrate 120 is formed from the same material as one or more ofportions 111, 113, and/or 115 can exhibit reduced reflection ofradiation at 11 at the interface between grating layer 110 and substrate120 relative, for example, to embodiments where substrate 120 is formedfrom a material that has a different refractive index to the materialsforming portions 111, 113, and/or 115.

The structure and composition of cap layer 130 can also vary as desired.In general, cap layer 130 (along the z-direction) is provided to protectgrating layer 110, encapsulating it from exposure to the environment. Incertain embodiments, cap layer 130 can provide additional functionality,such as providing an optical function and/or providing a substrate forone or more additional layers.

In certain embodiments, the top surface of cap layer 130 (i.e., thesurface opposite the interface between cap layer 130 and grating layer110) can be polished smooth. One or more additional layers can bedeposited on the top surface of cap layer 130.

Typically, where polarizer film 100 is a transmissive polarizer, caplayer 130 is transparent to light at wavelength λ₁, transmittingsubstantially all light impinging thereon at wavelength λ₁ (e.g., about90% or more, about 95% or more, about 97% or more, about 99% or more,about 99.5% or more).

In general, cap layer 130 can be formed from any material compatiblewith the manufacturing processes used to produce polarizer 100 thatprovides the desired optical and mechanical function for the layer. Insome embodiments, cap layer 130 can be formed from the same material asone or more portions 111, 113, and 115. In certain embodiments, caplayer 130 can be formed from the same material as substrate layer 120.

Cap layer 130, portions 111, 113, and 115, and substrate layer 120 canall be formed from materials that have the same or similar opticalproperties at λ₁. For example, these layers and portions can be formedfrom SiO₂ and/or materials with the same or similar optical propertiesas SiO₂ at λ₁. In such embodiments, overall transmission of radiation atλ₁ can be higher than in embodiments where one or more of the layers 120and 130 and/or portions 111, 113, and/or 115 are formed materials havediffering optical properties at λ₁.

Turning now to the theoretical performance of some exemplary structures,FIG. 1E-1G show plots of the optical properties of a grating layerhaving following structure summarized in Table II:

TABLE II Exemplary polarizer film parameters for simulation. p₁₁₀ 147 nmt₁₁₀ 180 nm Composition of lines 112 TiO₂ w₁₁₂ 7 nm Composition of lines114 TiO₂ w₁₁₄ 7 nm t₁₁₄ 160 nm Composition of portions 111 SiO₂ w₁₁₁ 29nm Composition of portions 113 SiO₂ w₁₁₃ 20 nm Composition of portions115 SiO₂ w₁₁₅ 50 nm Composition of substrate UV Grade Fused SilicaComposition of cap layer SiO₂

TABLE III Simulated optical performance for different incident angles.Incident Angle Extinction Ratio Pass state transmission  0° 28 dB 72.7% 5° 28 dB 71.5% 10° 27.9 dB 67.6% 15° 27.5 dB 61.8% 20° 27 dB 54.6%

All plots are for normally incident radiation. FIG. 1E shows theextinction ration as a function of wavelength for the wavelength rangefrom 200 nm to 500 nm. Peak extinction ratio of about 50 occurs around300 nm for the data points shown.

For the same wavelength range, FIG. 1F shows the total pass state energythat is either transmitted or reflected by the polarizer. Note here thatat shorter wavelengths, a relatively large amount of pass stateradiation is absorbed by the polarizer, hence a totaltransmitted/reflected energy of 0.5 or lower for wavelengths close to200 nm. Conversely, at wavelengths closer to 350 nm and above, thepolarizer absorption is relatively low, resulting in substantially allpass state radiation either being transmitted or absorbed by thepolarizer.

FIG. 1G shows pass state transmission for wavelengths from 200 nm to 500nm. At least 50% of pass state radiation is transmitted for wavelengthsabove 250 nm for the wavelength range shown.

Off axis optical performance was also calculated for the exemplarypolarizer film. Extinction ratio and pass state transmission for severalincident angles are shown in Table III. This data is calculated for awavelength of 266 nm.

The data in FIGS. 1E-1G were generated using the MATLAB gratingdiffraction calculator GD-Calc® obtained from KJ Innovation(http://software.kjinnovation.com/GD-Calc.html). For the purposes of thesimulations, the following refractive index data was used: for TiO₂,n=1.6 and k=3.2; and for SiO₂, n=1.5.

In general, linear polarizer film 100 can be prepared in a variety ofways. Generally, polarizer films are prepared using deposition andpatterning techniques commonly used in the fabrication of integratedcircuits. Deposition techniques that can be used include sputtering(e.g., radio frequency sputtering), evaporating (e.g., electron beamevaporation, ion assisted deposition (IAD) electron beam evaporation),or chemical vapor deposition (CVD) such as plasma enhanced CVD (PECVD),atomic layer deposition (ALD), or by oxidization. Patterning can beperformed using lithographic and etching techniques, such as electronbeam lithography, photolithography (e.g., using a photomask or usingholographic techniques), and imprint lithography. Etching techniquesinclude, for example, reactive ion etching, ion beam etching, sputteringetching, chemical assisted ion beam etching (CAIBE), or wet etching.

A discussion of techniques for forming grating structures that can beapplied to the structures described herein are discussed in U.S. PatentPublication No. US 2005-0277063 A1, entitled “OPTICAL FILMS AND METHODSOF MAKING THE SAME,” filed on May 27, 2005, the entire contents of whichis incorporated herein by reference. In some embodiments, multiplepolarizers can be prepared simultaneously by forming a relatively largegrating layer on a single substrate, which is then diced into individualunits. For example, a grating layer can be formed on a substrate thathas a single-side surface area about 10 square inches or more (e.g., afour inch, six inch, or eight inch diameter substrate). After formingthe grating layer, the substrate can be diced into multiple units ofsmaller size (e.g., having a single-side surface area of about onesquare inch or less).

Referring now to FIGS. 2A-2J, in some embodiments, a grating layer witha short effective period is formed by depositing a material onto theside walls of portions of a primary grating having a relatively longerperiod. FIG. 2A shows a cross-sectional view of a blank substrate 201 onwhich a grating layer is to be formed. Typically, blank substrate 201 isformed from the same material as the substrate layer. For example, blanksubstrate 201 can be a piece of silica or quartz.

Referring to FIG. 2B, in an initial step, a layer 202 of a resistmaterial is deposited onto a surface of blank substrate 201. In general,the type of resist is selected based its suitability for processing theblank substrate. In some embodiments, a polymeric resist can be used. Incertain embodiments, the resist is a metal, such as aluminum or chrome.Multilayer resists can be used.

Referring to FIG. 2C, layer 202 is patterned to provide a mask for blanksubstrate 201. The mask is depicted as portions 203 in FIG. 2C. Thewidth of portions 203 corresponds to the width of portions 115 in thegrating layer being formed.

After layer 202 is patterned, blank substrate 201 is etched to provideportions 115. Blank substrate 201 is etched a desired depthcorresponding to the thickness of the grating layer. In FIG. 2C, theblank substrate is etched to a depth indicated by line 121, whichrepresents the interface between substrate layer 120 and the gratinglayer which will be formed on the substrate layer.

Referring to FIG. 2D, the portions 203 of the resist mask are removed,leaving behind substrate layer 120 and portions 115.

Next, as shown in FIG. 2E, a conformal layer 210 of a first material isformed over portions 115 and in the trenches between these portions. Theconformal layer 210 forms a layer on the sidewalls of portions 115 thatis the same thickness as the layer deposited in the trenches between theportions and the layer formed on top of portions 115. Conformal layer210 is a precursor for grating lines 112. Accordingly, conformal layer210 is formed from the material used for grating lines 112 and thethickness of conformal layer 210 corresponds to the desired width ofgrating lines 112. In certain embodiments, atomic layer deposition isused to form conformal layer 210. Atomic layer deposition is describedin more detail below.

In a following step, with reference to FIG. 2F, the conformal layer isanisotropically etched, removing the portions of the layer betweenportions 115 and on top of portions 115, but leaving behind thesidewalls of portions 115. These sidewalls form grating lines 112. Forexample, reactive ion etching can be used. In some embodiments, reactiveion etching using oxygen and CHF3 gas (e.g., 0.5 sccm of O2 and 5 sccmof CHF3) with approximately 100-130 W power.

Following the etch step, a second conformal layer 220 is formed overportions 115, grating lines 112, and between the trenches betweengrating lines 112 as shown in FIG. 2G. Second conformal layer 220 is aprecursor for portions 113 and is therefore formed from the materialused for portions 113 and the thickness of conformal layer 220corresponds to the width of portions 113. In some embodiments, secondconformal layer is formed from a material having similar or identicaloptical properties to the material forming portions 115. Secondconformal layer 220 can also be formed using atomic layer deposition.

Next, referring to FIG. 2H, a third conformal layer 230 is formed oversecond conformal layer 220. Third conformal layer 230 is a precursor forgrating lines 114 and is formed from the material used for grating lines114. The thickness of conformal layer 230 corresponds to the width ofgrating lines 114.

Referring to FIG. 2I, in a further anisotropic etch step, portions ofsecond conformal layer 220 and third conformal layer 230 are removed,leaving behind portions 113 and grating lines 114, respectively. Incertain embodiments, third conform al layer 230 but not second conformallayer 220 is etched.

Finally, the remaining trenches between grating lines 114 are filled toprovide portions 111. Additional material is deposited over gratinglayer 110 to provide cap layer 130. In embodiments, the portions 111 andcap layer 130 are formed in a single deposition step. Either or both ofportions 111 and cap layer 130 can be formed using atomic layerdeposition.

In some embodiments, second conformal layer 220 is etched prior todeposition of third conformal layer 230. In such cases, grating lines114 have the same thickness as grating lines 112.

As discussed above, in some embodiments, certain portions of the gratinglayer and/or other layers are prepared using atomic layer deposition(ALD). Referring to FIG. 3, an ALD system 900 can be used to conformallydeposit material on an intermediate article 901. Conformal deposition byALD occurs monolayer by monolayer, providing substantial control overthe composition and thickness of the depositions. During deposition of amonolayer, vapors of a precursor are introduced into the chamber and areadsorbed onto exposed surfaces of article 901 or previously depositedmonolayers adjacent these surfaces. Subsequently, a reactant isintroduced into the chamber that reacts chemically with the adsorbedprecursor, forming a monolayer of a desired material. The self-limitingnature of the chemical reaction on the surface can provide precisecontrol of film thickness and large-area uniformity of the depositedlayer. Moreover, the non-directional adsorption of precursor onto eachexposed surface provides for uniform deposition of material onto theexposed surfaces, regardless of the orientation of the surface relativeto chamber B. Accordingly, the layers of the nanolaminate film conformto the shape of the trenches of intermediate article 901.

ALD system 900 includes a reaction chamber 910, which is connected tosources 950, 960, 970, 980, and 990 via a manifold 930. Sources 950,960, 970, 980, and 990 are connected to manifold 930 via supply lines951, 961, 971, 981, and 991, respectively. Valves 952, 962, 972, 982,and 992 regulate the flow of gases from sources 950, 960, 970, 980, and990, respectively. Sources 950 and 980 contain a first and secondprecursor, respectively, while sources 960 and 990 include a firstreagent and second reagent, respectively. Source 970 contains a carriergas, which is constantly flowed through chamber 910 during thedeposition process transporting precursors and reagents to article 901,while transporting reaction byproducts away from the substrate.Precursors and reagents are introduced into chamber 910 by mixing withthe carrier gas in manifold 930. Gases are exhausted from chamber 910via an exit port 945. A pump 940 exhausts gases from chamber 910 via anexit port 945. Pump 940 is connected to exit port 945 via a tube 946.

ALD system 900 includes a temperature controller 995, which controls thetemperature of chamber 910. During deposition, temperature controller995 elevates the temperature of article 901 above room temperature. Ingeneral, the temperature should be sufficiently high to facilitate arapid reaction between precursors and reagents, but should not damagethe substrate. In some embodiments, the temperature of article 901 canbe about 500° C. or less (e.g., about 400° C. or less, about 300° C. orless, about 200° C. or less, about 150° C. or less, about 125° C. orless, about 100° C. or less).

Typically, the temperature should not vary significantly betweendifferent portions of article 901. Large temperature variations cancause variations in the reaction rate between the precursors andreagents at different portions of the substrate, which can causevariations in the thickness and/or morphology of the deposited layers.In some embodiments, the temperature between different portions of thedeposition surfaces can vary by about 40° C. or less (e.g., about 30° C.or less, about 20° C. or less, about 10° C. or less, about 5° C. orless).

Deposition process parameters are controlled and synchronized by anelectronic controller 999. Electronic controller 999 is in communicationwith temperature controller 995; pump 940; and valves 952, 962, 972,982, and 992. Electronic controller 999 also includes a user interface,from which an operator can set deposition process parameters, monitorthe deposition process, and otherwise interact with system 900.

Referring to FIG. 4, the ALD process is started (1005) when system 900introduces the first precursor from source 950 into chamber 910 bymixing it with carrier gas from source 970 (1010). A monolayer of thefirst precursor is adsorbed onto exposed surfaces of article 901, andresidual precursor is purged from chamber 910 by the continuous flow ofcarrier gas through the chamber (1015). Next, the system introduces afirst reagent from source 960 into chamber 910 via manifold 930 (1020).The first reagent reacts with the monolayer of the first precursor,forming a monolayer of the first material. As for the first precursor,the flow of carrier gas purges residual reagent from the chamber (1025).Steps 1010 through 1025 are repeated until the layer of the firstmaterial reaches a desired thickness (1030).

In embodiments where the films are a single layer of material, theprocess ceases once the layer of first material reaches the desiredthickness (1035). However, for a nanolaminate film, the systemintroduces a second precursor into chamber 910 through manifold 930(1040). A monolayer of the second precursor is adsorbed onto the exposedsurfaces of the deposited layer of first material and carrier gas purgesthe chamber of residual precursor (1045). The system then introduces thesecond reagent from source 980 into chamber 910 via manifold 930. Thesecond reagent reacts with the monolayer of the second precursor,forming a monolayer of the second material (1050). Flow of carrier gasthrough the chamber purges residual reagent (1055). Steps 580 through510 are repeated until the layer of the second material reaches adesired thickness (1060).

Additional layers of the first and second materials are deposited byrepeating steps 1040 through 1055. Once the desired number of layers areformed (e.g., the trenches are filled and/or cap layer has a desiredthickness), the process terminates (1070), and the coated article isremoved from chamber 910.

Although the precursor is introduced into the chamber before the reagentduring each cycle in the process described above, in other examples thereagent can be introduced before the precursor. The order in which theprecursor and reagent are introduced can be selected based on theirinteractions with the exposed surfaces. For example, where the bondingenergy between the precursor and the surface is higher than the bondingenergy between the reagent and the surface, the precursor can beintroduced before the reagent. Alternatively, if the binding energy ofthe reagent is higher, the reagent can be introduced before theprecursor.

The thickness of each monolayer generally depends on a number offactors. For example, the thickness of each monolayer can depend on thetype of material being deposited. Materials composed of larger moleculesmay result in thicker monolayers compared to materials composed ofsmaller molecules.

The temperature of the article can also affect the monolayer thickness.For example, for some precursors, a higher temperature can reduceadsorption of a precursor onto a surface during a deposition cycle,resulting in a thinner monolayer than would be formed if the substratetemperature were lower.

The type or precursor and type of reagent, as well as the precursor andreagent dosing can also affect monolayer thickness. In some embodiments,monolayers of a material can be deposited with a particular precursor,but with different reagents, resulting in different monolayer thicknessfor each combination. Similarly, monolayers of a material formed fromdifferent precursors can result in different monolayer thickness for thedifferent precursors.

Examples of other factors which may affect monolayer thickness includepurge duration, residence time of the precursor at the coated surface,pressure in the reactor, physical geometry of the reactor, and possibleeffects from the byproducts on the deposited material. An example ofwhere the byproducts affect the film thickness are where a byproductetches the deposited material. For example, HCl is a byproduct whendepositing TiO₂ using a TiCl₄ precursor and water as a reagent. HCl canetch the deposited TiO₂ before it is exhausted. Etching will reduce thethickness of the deposited monolayer, and can result in a varyingmonolayer thickness across the substrate if certain portions of thesubstrate are exposed to HCl longer than other portions (e.g., portionsof the substrate closer to the exhaust may be exposed to byproductslonger than portions of the substrate further from the exhaust).

Typically, monolayer thickness is between about 0.1 nm and about fivenm. For example, the thickness of one or more of the depositedmonolayers can be about 0.2 nm or more (e.g., about 0.3 nm or more,about 0.5 nm or more). In some embodiments, the thickness of one or moreof the deposited monolayers can be about three nm or less (e.g., abouttwo nm, about one nm or less, about 0.8 nm or less, about 0.5 nm orless).

The average deposited monolayer thickness may be determined bydepositing a preset number of monolayers on a substrate to provide alayer of a material. Subsequently, the thickness of the deposited layeris measured (e.g., by ellipsometry, electron microscopy, or some othermethod). The average deposited monolayer thickness can then bedetermined as the measured layer thickness divided by the number ofdeposition cycles. The average deposited monolayer thickness maycorrespond to a theoretical monolayer thickness. The theoreticalmonolayer thickness refers to a characteristic dimension of a moleculecomposing the monolayer, which can be calculated from the material'sbulk density and the molecules molecular weight. For example, anestimate of the monolayer thickness for SiO₂ is ˜0.37 nm. The thicknessis estimated as the cube root of a formula unit of amorphous SiO₂ withdensity of 2.0 grams per cubic centimeter.

In some embodiments, average deposited monolayer thickness cancorrespond to a fraction of a theoretical monolayer thickness (e.g.,about 0.2 of the theoretical monolayer thickness, about 0.3 of thetheoretical monolayer thickness, about 0.4 of the theoretical monolayerthickness, about 0.5 of the theoretical monolayer thickness, about 0.6of the theoretical monolayer thickness, about 0.7 of the theoreticalmonolayer thickness, about 0.8 of the theoretical monolayer thickness,about 0.9 of the theoretical monolayer thickness). Alternatively, theaverage deposited monolayer thickness can correspond to more than onetheoretical monolayer thickness up to about 30 times the theoreticalmonolayer thickness (e.g., about twice or more than the theoreticalmonolayer thickness, about three time or more than the theoreticalmonolayer thickness, about five times or more than the theoreticalmonolayer thickness, about eight times or more than the theoreticalmonolayer thickness, about 10 times or more than the theoreticalmonolayer thickness, about 20 times or more than the theoreticalmonolayer thickness).

During the deposition process, the pressure in chamber 910 can bemaintained at substantially constant pressure, or can vary. Controllingthe flow rate of carrier gas through the chamber generally controls thepressure. In general, the pressure should be sufficiently high to allowthe precursor to saturate the surface with chemisorbed species, thereagent to react completely with the surface species left by theprecursor and leave behind reactive sites for the next cycle of theprecursor. If the chamber pressure is too low, which may occur if thedosing of precursor and/or reagent is too low, and/or if the pump rateis too high, the surfaces may not be saturated by the precursors and thereactions may not be self limited. This can result in an uneventhickness in the deposited layers. Furthermore, the chamber pressureshould not be so high as to hinder the removal of the reaction productsgenerated by the reaction of the precursor and reagent. Residualbyproducts may interfere with the saturation of the surface when thenext dose of precursor is introduced into the chamber. In someembodiments, the chamber pressure is maintained between about 0.01 Torrand about 100 Torr (e.g., between about 0.1 Torr and about 20 Torr,between about 0.5 Torr and 10 Torr, such as about 1 Torr).

Generally, the amount of precursor and/or reagent introduced during eachcycle can be selected according to the size of the chamber, the area ofthe exposed substrate surfaces, and/or the chamber pressure. The amountof precursor and/or reagent introduced during each cycle can bedetermined empirically.

The amount of precursor and/or reagent introduced during each cycle canbe controlled by the timing of the opening and closing of valves 952,962, 982, and 992. The amount of precursor or reagent introducedcorresponds to the amount of time each valve is open each cycle. Thevalves should open for sufficiently long to introduce enough precursorto provide adequate monolayer coverage of the substrate surfaces.Similarly, the amount of reagent introduced during each cycle should besufficient to react with substantially all precursor deposited on theexposed surfaces. Introducing more precursor and/or reagent than isnecessary can extend the cycle time and/or waste precursor and/orreagent. In some embodiments, the precursor dose corresponds to openingthe appropriate valve for between about 0.1 seconds and about fiveseconds each cycle (e.g., about 0.2 seconds or more, about 0.3 secondsor more, about 0.4 seconds or more, about 0.5 seconds or more, about 0.6seconds or more, about 0.8 seconds or more, about one second or more).Similarly, the reagent dose can correspond to opening the appropriatevalve for between about 0.1 seconds and about five seconds each cycle(e.g., about 0.2 seconds or more, about 0.3 seconds or more, about 0.4seconds or more, about 0.5 seconds or more, about 0.6 seconds or more,about 0.8 seconds or more, about one second or more).

The time between precursor and reagent doses corresponds to the purge.The duration of each purge should be sufficiently long to removeresidual precursor or reagent from the chamber, but if it is longer thanthis it can increase the cycle time without benefit. The duration ofdifferent purges in each cycle can be the same or can vary. In someembodiments, the duration of a purge is about 0.1 seconds or more (e.g.,about 0.2 seconds or more, about 0.3 seconds or more, about 0.4 secondsor more, about 0.5 seconds or more, about 0.6 seconds or more, about 0.8seconds or more, about one second or more, about 1.5 seconds or more,about two seconds or more). Generally, the duration of a purge is about10 seconds or less (e.g., about eight seconds or less, about fiveseconds or less, about four seconds or less, about three seconds orless).

The time between introducing successive doses of precursor correspondsto the cycle time. The cycle time can be the same or different forcycles depositing monolayers of different materials. Moreover, the cycletime can be the same or different for cycles depositing monolayers ofthe same material, but using different precursors and/or differentreagents. In some embodiments, the cycle time can be about 20 seconds orless (e.g., about 15 seconds or less, about 12 seconds or less, about 10seconds or less, about 8 seconds or less, about 7 seconds or less, about6 seconds or less, about 5 seconds or less, about 4 seconds or less,about 3 seconds or less). Reducing the cycle time can reduce the time ofthe deposition process.

The precursors are generally selected to be compatible with the ALDprocess, and to provide the desired deposition materials upon reactionwith a reagent. In addition, the precursors and materials should becompatible with the material on which they are deposited (e.g., with thesubstrate material or the material forming the previously depositedlayer). Examples of precursors include chlorides (e.g., metalchlorides), such as TiCl₄, SiCl₄, SiH₂Cl₂, TaCl₃, HfCl₄, InCl₃ andAlCl₃. In some embodiments, organic compounds can be used as a precursor(e.g., Ti-ethaOxide, Ta-ethaOxide, Nb-ethaOxide). Another example of anorganic compound precursor is (CH₃)₃Al. For SiO₂ deposition, forexample, suitable precursors include Tris(tert-butoxy),Tris(tert-pentoxy) silanol, or tetraethoxysilane (TEOS).

The reagents are also generally selected to be compatible with the ALDprocess, and are selected based on the chemistry of the precursor andmaterial. For example, where the material is an oxide, the reagent canbe an oxidizing agent. Examples of suitable oxidizing agents includewater, hydrogen peroxide, oxygen, ozone, (CH₃)₃Al, and various alcohols(e.g., Ethyl alcohol CH₃OH). Water, for example, is a suitable reagentfor oxidizing precursors such as TiCl₄ to obtain TiO₂, AlCl₃ to obtainAl₂O₃, and Ta-ethaoxide to obtain Ta₂O₅, Nb-ethaoxide to obtain Nb₂O₅,HfCl₄ to obtain HfO₂, ZrCl₄ to obtain ZrO₂, and InCl₃ to obtain In₂O₃.In each case, HCl is produced as a byproduct. In some embodiments,(CH₃)₃Al can be used to oxidize silanol to provide SiO₂.

While the foregoing discussion of polarizer film 100 and associatedmanufacturing methods refer to the embodiment shown in FIGS. 1A-1C, ingeneral, other embodiments are also possible. For example, embodimentsof polarizing films can include additional layers to grating layer 110,substrate layer 120, and cap layer 130. Referring to FIG. 5, forexample, a polarizer film 300 includes an etch stop layer 320 between asubstrate layer 310 and grating layer 110.

Etch stop layer 320 is formed from a material resistant to etchingprocesses used to etch the material(s) from which portions 115 and/orgrating lines 112 and/or 114 are formed. The material(s) forming etchstop layer 320 should also be compatible with substrate layer 310 andwith the materials forming grating layer 110. Examples of materials thatcan form etch stop layer 320 include HfO₂, SiO₂, Ta₂O₅, TiO₂, SiN_(x),or metals (e.g., Cr, Ti, Ni).

The thickness of etch stop layer 320 can be varied as desired.Typically, etch stop layer 320 is sufficiently thick to preventsignificant etching of substrate layer 310, but should not be so thickas to adversely impact the optical performance of polarizer film 300. Insome embodiments, etch stop layer 320 is about 500 nm or less (e.g.,about 250 nm or less, about 100 nm or less, about 75 nm or less, about50 nm or less, about 40 nm or less, about 30 nm or less, about 20 nm orless).

In some embodiments, polarizer films can include further additionallayers. For example, antireflection films on one or both surfaces of apolarizer film can reduce the reflectance of pass state light ofwavelength λ₁ impinging on and/or exiting a polarizer film.Antireflection films generally include one or more layers of differentrefractive index. As an example, antireflection films can be formed fromfour alternating relatively high and relatively low index layers. Therelatively high index layers can be formed, for example, from TiO₂ orTa₂O₅ and the relatively low index layers can be formed, for example,from SiO₂ or MgF₂. The antireflection films can be broadbandantireflection films or narrowband antireflection films.

In some embodiments, polarizer films have a reflectance of about 5% orless of light impinging thereon at wavelength λ for pass statepolarization (e.g., about 3% or less, about 2% or less, about 1% orless, about 0.5% or less, about 0.2% or less).

While grating layer 110 in polarizer films 100 and 300 is a monolithiclayer (i.e., there are no gaps between the different portions of thelayer), embodiments can include some portions or grating lines that areadjacent to gaps. For example, referring to FIG. 6, a polarizer film 400includes a grating layer 410 in which each grating line 112 and 114 isadjacent a portion 113 formed from a different material on one side, andadjacent a gap 411 or 415 on the opposite side. In the context of thegrating layer formation process discussed above, such a grating layercan be formed, for example, by not depositing portions 111 and byetching away portions 115 after formation of grating lines 112 and 114.

In certain embodiments, only grating lines 114 are adjacent gaps, whilegrating lines 112 are separated by portions of a solid material. Such agrating layer can be formed, for example, by not depositing portions 111or cap layer 130 over the grating layer. Alternatively, in someembodiments, grating lines 112 are adjacent solid portions while gratinglines 114 are separated by gaps. This can be accomplished by etchingportions 115 after depositing portions 111, for example.

The grating layers in polarizer films 100, 300, and 400 each include arepeating structure that includes four grating lines (i.e., two gratinglines 112 and two grating lines 114). More generally, grating layers caninclude repeating structures having more than four grating lines. Forexample, referring to FIGS. 7A and 7B, a polarizer film 700 includes agrating layer 710 that has a repeating structure that includes sixgrating lines, including two grating lines 712, two grating lines 714,and two grating lines 716. The repeating structure has a pitch p₇₁₀, andthe grating lines have an effective period Λ₇₁₀ equal to p₇₁₀/6.

Referring back to FIGS. 2A-2J, additional grating lines can be formed,for example, by depositing additional conformal layers over portions115, grating lines 112, portions 113, and grating lines 114, andsubsequently anisotropically etching the additional conformal layersbefore depositing portions 111.

Additional grating lines can be formed by repeating this process asnecessary. For example, in certain embodiments, each repeating structurein a grating layer can include eight grating lines, ten grating lines,or more.

While certain embodiments have been described, in general, other linearpolarizer structures are also possible. For example, while FIGS. 1A-1C,5, 6, 7A and 7B show a variety of configurations of polarizer films,other embodiments can include additional or fewer layers. For example,in some embodiments, polarizers can also include protective layers, suchas hardcoat layers (e.g., hardcoat polymers).

Furthermore, while embodiments of polarizers have been described thatinclude a grating layer that has grating lines with a rectangulargrating profile, other embodiments are also possible. For example, insome embodiments, the grating layer have a curved profile, such as asinusoidal profile. Alternatively, the grating layer can have atriangular profile, sawtooth profile, or trapezoidal profile. Moreover,in general, the profile of grating layers may vary slightly from itsdesignated geometry (e.g., rectangular, triangular, trapezoidal) due toimperfections associated with the manufacturing process.

Polarizer films such as those described herein can be incorporated intooptical devices, including passive optical devices (e.g., polarizingdevices) and active optical devices (e.g., liquid crystal displays).Polarizer films can be integrated into the device, providing amonolithic device, or can be arranged separately from other componentsof the device.

In certain embodiments, polarizer films can be used in applications toprovide polarized UV radiation to a substrate. Referring to FIG. 8, a UVexposure system 1200 includes a UV source 1210, a polarizer film 1220,and a substrate support 1230 configured to position a substrate 1240 toreceive radiation from UV source 1210. Radiation 1211 emitted fromsource 1210 passes through polarizer film 1220, emerging as polarizedradiation 1212 directed to substrate 1240. Optionally, system 1200 caninclude optical elements between source 1210 and polarizer film 1220and/or between polarizer film 1220 and substrate 1240. The opticalelements can be used to control (e.g., homogenize) the illumination ofthe substrate by source 1210. As an example, in some embodiments, UVexposure system 1200 can be used to expose liquid crystal alignmentlayers, e.g., on a surface of an LCD panel.

As another example, polarizer films can be used in lithography exposuretools that utilize UV radiation to expose resist layers on wafers or LCDsubstrates. For example, polarizer films can be produced to operate atwavelengths commonly used in lithography tools, such as 248 nm, 193 nm,and/or 157 nm. Polarizers can be included in the illumination systems(optical systems for delivering radiation from a light source to areticle) and/or projection systems (optical system for imaging thereticle onto a resist on a substrate) of lithography tools.

UV polarizers can also be used in the metrology system for waferinspection (e.g., such as in commercially-available metrology systemslike the Surfscan systems available from KLA-Tencor, San Jose, Calif.),where narrowband UV light (e.g., at about 266 nm) and/or broadband UVlight (e.g., from about 240 nm to about 450 nm) is used to illuminatewafers and detect light reflected from the wafers, Information about thewafers can be determined based on the reflected light. UV polarizers canbe used to polarize the incident illumination and/or analyze thereflected illumination, thereby providing polarization-dependentinformation about the wafer and/or enhancing the resolution of thesystem relative to systems that utilize unpolarized light.

A number of embodiments have been described. Other embodiments are inthe following claims.

1. A method, comprising: providing a layer comprising a plurality ofspaced-apart lines of a first material extending along a firstdirection; forming a line of a second material on opposing surfaces ofeach line of the first material, the first and second materials beingdifferent and adjacent lines of the second material being discontinuous;after forming the lines of the second material, forming pairs ofspaced-apart lines of a third material between adjacent pairs of thelines of the second material, wherein each line of the third material isspaced apart from the closest line of the second material and the firstand third materials are different.
 2. The method of claim 1, wherein thelines of the first material have a pitch of 200 nm or less.
 3. Themethod of claim 1, wherein forming the lines of the second materialcomprises: forming a continuous layer of the second material on thelayer comprising the lines of the first material; and removing portionsof the continuous layer of the second material to provide the lines ofthe second material.
 4. The method of claim 3, wherein the continuouslayer of the second material is formed using atomic layer deposition. 5.The method of claim 3, wherein the continuous layer of the secondmaterial conforms to the surface profile of the layer comprising theplurality of lines of the first material.
 6. The method of claim 3,wherein removing the portions of the continuous layer of the secondmaterial comprises etching the layer of the second material.
 7. Themethod of claim 1, wherein the second material has a refractive index of1.8 or more and an extinction coefficient of 1.8 or more for awavelength λ that is 400 nm or less.
 8. The method of claim 1, whereinthe lines of the second material have a line width of 20 nm or less. 9.The method of claim 1, wherein the lines of the second material have athickness of 100 nm or more.
 10. The method of claim 1, wherein thelines of the second material have an aspect ratio of 5:1 or more. 11.The method of claim 1, wherein forming the lines of the third materialcomprises: forming a continuous layer of a fourth material over thelines of the second material; and forming a layer of the third materialover the layer of the fourth material, wherein the second and thirdmaterials are different from the fourth material.
 12. The method ofclaim 11, wherein forming the lines of the third material furthercomprises removing portions of the continuous layer of the thirdmaterial to provide the lines of the third material.
 13. The method ofclaim 1, wherein the third material is the same as the second material.14. The method of claim 1, wherein the second material has a refractiveindex of 1.8 or more and an extinction coefficient of 1.8 or more for awavelength λ that is 400 nm or less.
 15. The method of claim 1, whereinthe lines of the third material have a line width of 20 nm or less. 16.The method of claim 1, wherein the lines of the third material have athickness that is different from a thickness of the lines of the secondmaterial.
 17. The method of claim 16, wherein the thickness of the linesof the second material is greater than the thickness of the lines of thethird material.
 18. The method of claim 1, further comprising depositingfifth material over the lines of the third material, wherein the firstmaterial and the third material are different.
 19. The method of claim18, wherein the first material is the same as the fifth material. 20.The method of claim 18, wherein the fifth material is deposited usingatomic layer deposition.
 21. The method of claim 18, wherein depositingthe fifth material fills spaces between adjacent lines of the thirdmaterial.
 22. The method of claim 21, wherein depositing the fifthmaterial forms a monolithic layer comprising the fifth material, thelines of the second material, and the lines of the third material. 23.The method of claim 1, wherein providing the layer comprising the linesof the first material comprises providing a continuous layer of thefirst material and removing portions of the first material from thecontinuous layer to provide the lines of the first material.
 24. Themethod of claim 1, wherein the lines of the second and third materialsform a grating that transmits 20% or more of light of wavelength λhaving a first polarization state incident on the layer along a path,transmits 2% or less of light of wavelength λ having a secondpolarization state incident on the layer along the path, the first andsecond polarization states being orthogonal, and λ is 400 nm or less.25. The method of claim 24, wherein the grating has an extinction ratioof 20 dB or more for light at λ transmitted by the grating.
 26. Themethod of claim 24, wherein λ is in a range from 100 nm to 400 nm. 27.The method of claim 24, wherein λ is about 266 nm, about 248 nm, about193 nm, or about 157 nm.
 28. The method of claim 1, wherein the pairs ofspaced-apart lines of the third materials are formed between alternatingpairs of the lines of the second material.
 29. The method of claim 28,wherein the lines of the first material are positioned between pairs oflines of the second material between which no lines of the thirdmaterial are formed.
 30. A method, comprising: forming a first conformallayer of a first material over a first grating comprising a plurality oflines of the second material different from the first material; removingportions of the first conformal layer to provide a second gratingcomprising lines of the first material; forming a second conformal layerof a third material over the second grating; and removing portions ofthe second conformal layer to provide a third grating comprising linesof the third material and the lines of the first material, wherein thethird grating transmits 20% or more of light of wavelength λ having afirst polarization state incident on the layer along a path, transmits2% or less of light of wavelength λ having a second polarization stateincident on the layer along the path, the first and second polarizationstates being orthogonal, and λ is 400 nm or less.
 31. An article,comprising: a layer extending in a plane, the layer comprising: aplurality of spaced-apart lines of a first material extending along afirst direction in the plane, each of the lines of the first materialhaving a thickness, t₁, along a second direction perpendicular to theplane; a plurality of spaced-apart lines of a second material extendingalong the first direction, each of the lines of the second materialhaving a thickness, t₂, along the second direction, t₂ being less thant₁, and each line of the second material being spaced-apart from aclosest line of the first material, wherein the first and secondmaterials have a respective refractive index of 1.8 or more and arespective extinction coefficient of 1.8 or more for a wavelength λ thatis 400 nm or less, and the layer transmits 20% or more of light ofwavelength λ having a first polarization state incident on the layerperpendicular to the plane, transmits 2% or less of light of wavelengthλ having a second polarization state incident on the layer along thepath, the first and second polarization states being orthogonal.
 32. Asystem, comprising: a light source configured to provide radiation at awavelength λ during operation of the system; a support apparatusconfigured to position a substrate to receive radiation provided by thelight source; and a polarizer positioned between the light source andthe target, the polarizer comprising the article of claim 31.